Composition comprising unsaturated elastomer,epoxy resin polycarboxylic acid or anhydride,cross-linking catalyst and filler and golf ball made therefrom

ABSTRACT

A composition of matter particularly suitable for the manufacture of unitary molded golf balls consists of a blend of an unsaturated elastomer capable of being crosslinked by peroxide-initiated polymerization, an epoxy resin, a curing agent comprising unsaturated polycarboxylic acid or unsaturated polycarboxylic acid anhydride, a crosslinking catalyst for the elastomer and a filler material.

United States Patent Nesbitt [54] COMPOSITION COMPRISING UNSATURATEDELASTOMER, EPOXY RESIN POLYCARBOXYLIC ACID OR ANHYDRIDE, CROSS-LINKINGCATALYST AND FILLER AND GOLF BALL MADE THEREFROM [72] Inventor: RobertDennis Nesbitt, Don Mills, Ontario,

Canada [73] Assignee: Campbell Manufacturing Company Limited, Montreal,Quebec, Canada 22 Filed: Dec. 16, 1970 [21] Appl. No.: 98,930

Related US. Application Data [63] Continuation-impart of Ser. No.833,794, June 16,

1969, abandoned.

[30] Foreign Application Priority Data March 10, 1969 Canada ..O45,249

[52] US. Cl ..260/23.5 A, 260/23.7 M, 260/4l.5 R,

260/41.5 A, 260/47 EA, 260/78.4 D, 260/836, 260/837 R, 273/62, 273/218,273/DlG. 3, 273/D1G. 10

[ June 20, 1972 [51] Int. Cl ..A63b 37/00, C08d 9/08, C08d 9/ 10 [58]Field ofSearch ..260/47 EA, 836, 837 R, 23.5 A, 260/23.7 M, 41.5 R, 41.5A, 78.4 D; 273/62, 218

[56] References Cited UNITED STATES PATENTS 3,553,159 1/1971 Miller eta]. ..260/837 FOREIGN PATENTS OR APPLICATIONS 693,098 8/1964 Canada..260/837 920,802 3/1963 Great Britain .....260/837 1,051,030 12/ 1 966Great Britain ..260/837 Primary Examinen-Donald E. Czaja AssistantExaminer-Donald J. Barrack AttorneyGuy Drouin [57] ABSTRACT Acomposition of matter particularly suitable for the manufacture ofunitary molded golf balls consists of a blend of an unsaturatedelastomer capable of being crosslinked by peroxideinitiatedpolymerization, an epoxy resin, a curing agent comprising unsaturatedpolycarboxylic acid or unsaturated polycarboxylic acid anhydride, acrosslinking catalyst for the elastomer and a filler material.

14 Claims, No Drawings COMPOSITION COMPRISING UNSATURATED ELASTOMER,EPOXY RESIN POLYCARBOXYLIC ACID OR ANl-IYDRIDE, CROSS-LINKING CATALYSTAND FILLER AND GOLF BALL MADE THEREFROM This application is acontinuation-in-part of application, Ser. No. 833,794 filed on June 16,1969 and now abandoned.

This invention relates to a novel composition of matter and is moreparticularly directed to an improved unitary molded golf ball madetherefrom. The golf ball of the invention exhibits exceptional cut andimpact resistance yet retains all of the desirable characteristics ofthe conventional rubber thread wound ball.

Prior art golf balls comprise, in general, two types. These are thewound ball, wherein a vulcanized rubber string is wound under tensionabout a solid or semi-solid core and thereafter enclosed in a sheath orcovering of tough, protective material. The second known prior art golfball consists of a solid mass of moldable resilient material which hasbeen cured to develop the necessary degree of hardness to provideutility. Generally such molded balls require no enclosing cover. Boththe wound ball and the molded ball must conform to standards of ballsize, weight, roundness, initial velocity and click as set down in therules of play by, for example, the United States Golf Association(U.S.G.A.

While the wound ball has for many years satisfied both the standards ofthe U.S.G.A. and the requirements of most players of the game of golf,it has not been without disadvantages. The wound ball of good quality isdifiicult to manufacture due to the number of production steps requiredand the careful control which must be exercised in each stage ofmanufacture in order to achieve suitable roundness, velocity or rebound,click" and the like. Click is the term applied to the sound produced bythe ball when dropped on a hard surface or when struck with a golf club.As well, the cover material for the wound ball has not provided theoptimum in adhesion to the wound core and is also frequently susceptibleto cutting when struck by the club.

In an effort to overcome the shortcomings of the wound ball, theone-piece molded ball was developed. Such a ball generally comprises acombination of materials such as elastomers, fillers and curing agentswhich may be formed under high pressure and temperature to provide aball of suitable hardness and resilience. Molded balls are described,for example, by J. R. Bartsch in U.S. Pat. No. 3,313,545, G. H. Brice inUS. Pat. No. 3,373,123 and H. W. Brandt et al. in US. Pat. No.3,384,612.

Whereas the production of molded balls has involved simplifiedmanufacturing procedures and has resulted in reduced production costs,these balls have not proven completely successful in respect to cutresistance, water absorption and resilience.

It is, therefore, the primary object of this invention to provide aunitary molded golf ball of improved cut resistance, which ball complieswith all the requirements of the rules of golf play. Additional objectsof the invention will appear hereinafter.

The improved golf ball of the present invention comprises a molded blendof an elastomer capable of being crosslinked by peroxide-initiatedpolymerization, an epoxy resin, an epoxy resin curing agent or hardenercomprising unsaturated polycarboxylic acids, unsaturated polycarboxylicacid anhydrides and mixtures thereof, a filler material, a crosslinkingcatalyst for said elastomer and, optionally, an epoxy resin curingaccelerator.

The important discovery of the present invention which distinguishes thecomposition of matter from the prior art and which results in markedlyimproved cut and impact resistance in golf balls and other shapedobjects made-therefrom is the use as the epoxy resin curing agent orhardener of unsaturated polycarboxylic acids, unsaturated polycarboxylicacid anhydrides and mixtures thereof. The use of such hardener enablesthe elastomeric polymer component and the epoxy resin polymer componentto bond together forming strong chemical bonds.

It is well known from the prior art that epoxy resins will react withother materials to form hard, resinous products. Some of these epoxyresin hardeners or curing agents include, for example, primary,secondary and tertiary amines and Lewis acids. It has now been foundthat if an epoxy resin curing agent is chosen which contains reactiveunsaturation and this curingagent is employed in a mixture of epoxyresin and unsaturated elastomer capable of being crosslinked, theresulting curing reaction produces a multi-dimensional system havingstrong interlocking bonds. The hardened epoxy resin produces in aresultant golf ball made therefrom the desired hardness and click" whilethe crosslinked elastomer contributes high resilience and rebound. Bothsystems are held together in a single matrix to provide a molded ball ofextreme durability. However, if an epoxy resin curing agent is chosenwhich lacks reactive unsaturation, the resultant product, while havingsome of the characteristics of a conventional wound ball, will lackclick and shows no improvement in cut or im pact resistance due to theabsence of chemical bonding between the epoxy system and the elastomersystem.

The preferred elastomer capable of being crosslinked by peroxideinitiation in the composition of the invention is cis- 1,4-polybutadienebecause of its very high resiliency and low hysteresis. Other elastomerswhich may be used, although these generally will be employed in lowergrade or lower quality balls, include, for example, polyisoprene,ethylene/propylene/non-conjugated diolefin terpolymers,styrene/butadiene rubbers, acrylonitrile/butadiene copolymers andmixtures thereof.

As epoxy resin, it is preferred to use cycle-aliphatic epoxy resins andparticularly those cyclo-aliphatic epoxy resins which have low molecularweight because of ease of processing during manufacture and because highcrosslinking density and fast cure rates may be obtained during theiruse. By low molecular weight is meant an epoxy resin having a viscosityof less than 1,000 cps. when measured at 25 C.

Examples of cycloaliphatic epoxy resins which have been foundparticularly suitable are those manufactured by Union Carbide Companyand sold under the designations ERL-4289 and ERL-422 l.

ERL-4289 has the structural formula and is characterized in having aviscosity of 900 cps. at 25 C. and an equivalent weight of 220.

ERL-422l which is most preferred for use in the composition of thisinvention is represented by the formula3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and isobtained by reacting, under mild conditions,3-cyclohexenylmethyl-3-cyclohexenecarboxylate with 2 moles of peraceticacid in solution. The carboxylate reactant is in turn obtained by theTischenko condensation of tetrahydrobenzaldehyde. ERL-4221 ischaracterized by a viscosity of 400 cps. at 25 C. and an equivalentweight of 135.

Other suitable epoxy resins include for example, epoxy novolac resinsand epichlorohydrin-4,4-dihydroxydiphenyldimethylmethane type resins.The latter type resins are polymers produced by condensation ofepichlorohydrin with 4,4-dihydroxyphenyl-dimethylmethane. A resin ofthis type, which has been found particularly suitable is one having amolecular weight of about 380. Epoxy novolac resins are produced bycondensing the hydroxyl group of a phenolic resin with epichlorohydrin.A suitable epoxy novolac resin is that having a viscosity of 14-20poises at 52 C. and an equivalent weight of 172-1 79.

The epoxy novolac resins and epichlorohydrin-4,4'-dihydroxyphenyl-dimethylmethane type resins are, however, more suitablefor use in applications other than golf balls due to the softer and moreflexible product which results from their combination with anunsaturated rubber and an unsaturated polycarboxylic acid or anhydride.Curing time is longer than with a cycle-aliphatic epoxy resin due to theslower reaction with rubber and curing agent.

Either high or low molecular weight resins may be employed depending onthe product being made and the intended end use of that product.Generally, low molecular weight resins result in a harder and lessflexible product than do the high molecular weight resins whencompounded with elastomer using an equal volume of resin. Greaterhardness may be obtained with the high molecular weight resins byincreasing the proportion of resin in the formulation. Such an increase,however, reduces the elastomer content and lowers the resilience of thefinal product.

The epoxy resin curing agents as mentioned heretofore are unsaturatedpolycarboxylic acids and their anhydrides such as, for example,citraconic acid, itaconic acid, fumaric acid, maleic acid and maleicanhydride. These agents may be used singly or in admixture with eachother.

The crosslinking catalyst is of the free radical or peroxide type suchas, for example, 2,5-bis(tert-butyl peroxy)-2,5- dimethylhexane,di-tert.butyl peroxide, dicumyl peroxide, benzoyl peroxide and2,4-dichlorobenzol peroxide.

Filler material used to control the weight of the molded ball withoutaffecting ball resilience is preferably a precipitated hydrated silicasuch as that sold under the trade mark HiSil" by the Pittsburg PlateGlass Company. Other suitable fillers include for example, clays, talc,asbestos, glass, carbonates such as calcium carbonate, magnesiumcarbonate, etc., metal oxides such as zinc oxide, iron oxide, aluminumoxide, magnesium oxide, etc., particulate synthetic plastics such ashigh molecular weight polyethylene, polystyrene, polyethylene ionomerresins, etc. and particulate carbonaceous materials such as carbonblack, natural bitumen, etc.

Additionally, the composition may also contain various additives wellknown in the rubber and molding arts such as, for example, crosslinkingpromoters for the elastomer, antioxidants, mold release agents and thelike.

Epoxy resin curing accelerators may be employed in small amounts tospeed up the curing rate of the epoxy resin and so match thecrosslinking rate of the elastomer component within the matrix. Theseepoxy curing accelerators may be any one of a number of well knowncommercial products adapted for this purpose and include, for example,stannous octoate, dimethylaminomethylphenol,tri(dimethylaminomethyl)phenol, Lewis acids such as boron trifluoridecomplexes, and the like.

The composition may also advantageously contain a white coloring pigmentsuch as for example, titanium dioxide, the presence of which simplifiesthe surface painting operation of the finished ball. in some cases theuse of coloring pigment will eliminate the need for painting altogether,such as, for example, where the ball is intended for use on drivingranges.

The preferred ranges of proportions of the ingredients used in thecomposition of the invention are shown below in Table l, the quantitiesshown being in parts by weight.

TABLE I Elastomer 100 Filler 20-45 Coloring Pigment (optional) 0.5-Epoxy Resin 20-45 Epoxy Resin Curing Agent 5-20 Epoxy Resin CuringAccelerator 0.1-0.5

(optional) Additives (antioxidants, mold release 0.5-5

agents, etc.) (optional) Crosslinking Qatalyst 0.5-5

Wide latitude may be taken in the production of balls from theingredients shown in Table l in order to provide balls of variouscompressions suitable for every type of golfer yet complying with allthe requirements of the standard ball as laid down in the rules of thegame. For example, low compression balls are generally preferred by thesoft" hitters or lady golfers and may be made by increasing theproportion of the elastomer component or by employing an elastomerhaving a lower resilience. Medium compression balls, preferred by theaverage golfers, may be made by carefully balancing the quantity of theelastomer and epoxy resin component, while high compression ballspreferred by the hard" hitters may be made by increasing the proportionof the epoxy resin component. Additionally, balls of various compressionmay be produced by controlling the degree of cure during themanufacturing process.

The golf ball of this invention may be made by following theconventional mixing and compounding procedures used in the rubberindustry. A typical mixing procedure consists of the followingsequential steps.

a. The epoxy resin component and the filler material are blendedtogether in a conventional mechanical mixer such as a Baker-Perkinsmixer.

b. The blended epoxy resin and filler are added to the elastomercomponent and blended together either in a mechanical mixer or on atwo-roll mill.

c. The remaining ingredients comprising the epoxy resin hardener, thecrosslinking catalyst, the epoxy resin curing accelerator, additivessuch as the mold release agent and the like, and, if desired, thecoloring pigment are added to the blended elastomer/epoxy resin/fillerand the whole mixed until homogeneous.

d. The fully blended mix may then be divided into small proportions ofdesired size and shape preparatory to the molding step. I

Molding of the ball is accomplished by placing the uncured, preformedportions or slugs'between the two halves of a conventional press moldhaving dimpled golf ball cavities therein and applying sufficientpressure to close the two halves of the mold. The volume of thepreformed portions placed in the mold cavities is slightly in excess ofthe actual volume of the ball cavities thus allowing the cavities to becompletely filled when the mold is closed. An extrudate or flash ofexcess molding composition is formed at the mating surfaces of the twoclosed hemispherical cavities. The pressure applied to the mold is thatwhich is required to close the mold completely during the cross-linkingand curing process and is optimumly from about 800 to 900 psi. for eachball molded. The molding temperature will primarily depend upon thedecomposition'temperature of the crosslinking catalyst employed. Theinitial decomposition of the preferred peroxide crosslinker,2,5-bis(tert-butyl peroxy)-2,S-dimethylhexane, is between 300 F. and 340F. Where this material is employed, the minimum molding temperature willbe 300 F. with the optimum temperature of about 310 F. High curingtemperatures up to 400 F. or higher are possible but are not desirablesince the cure rate is accelerated too quickly and the outside of themolded ball may become fully cured before the inside of the ball hasreached curing temperatures, thus preventing a homogeneous crosslinkeddensity throughout the ball. The curing time required with the preferredperoxide cross linker at a temperature of 310 F. is between about l0 and15 minutes. Normally no advantages will be gained in the physicalproperties of the ball if curing is extended beyond 15 minutes.

After the elapsed curing period, the mold cavities are cooled whilepressure is maintained on the mold platen. Slight shrinkage of thecured, molded ball occurs during cooling and permits easy removal of thecured ball from the mold. The mold cavity size is designed to accountfor this shrinkage and thus produce a ball having a minimum finisheddiameter of 1.680 inches as specified by the U.S.G.A. rules or, ifdesired, having a finished diameter of 1.62 inches for use in play underthe rules of The Royal and Ancient Golf Club of St. Andrews.

After being taken from the mold, the cured ball is trimmed or buffed toremove any parting seam or flash which may be fonned at theparting jointof the hemispherical mold cavities. The ball may then be painted andlabeled using conventional equipment employed in the industry.

The following Table ll. shows three compositions prepared in accordancewith the present invention and made up of the same constituents indifferent proportions so as to result in golf balls of 80, 90 and 100compression respectively.

Table Ill demonstrates the improved cut and impact resistance of thegolf balls of Table ll while maintaining the weight, rebound and click"properties of conventional wound balls.

The results shown in Table III are produced using two testing procedurescommonly employed in the golf ball industry. The first of these is theGuillotine Cut Test" wherein the ball to be tested is held firmly in acavity which exposes the top half of the ball. guillotine blade weighing5 pounds and having inner and outer blade edge angles of 90 and 60respectively and a cutting edge of three sixty-fourths inch radius isdropped from a height of 3.5 feet to strike the ball at a point one-halfinch off the top center point. The guillotine blade is guided during thedrop by means of a substantially frictionfree vertical track. The dropsare repeated until ball failure results, ball failure being defined aspermanent damage evidenced by a crack or by removal of a segment fromthe ball surface. The second test procedure employed is the Pneumaticlmpact Test wherein the ball is propelled by means of compressed airthrough a barrel having a length of 8 feet and against a slightlydeflected steel plate. The bore of the barrel is 1.695 inches, slightlyin excess of the U.S.G.A. standard maximum ball diameter. In the test,the ball is placed in the breech of the barrel to which is connected a16 gallon air reservoir containing air at p.s.i. Upon the opening of a1% inch quick-acting valve, the compressed air accelerates the ballthrough the barrel and against the steel plate placed a distance of llfeet from the breech. The test is repeated until ball failure results,failure being defined as surface breakage, removal of a surface segmentof permanent distortion of the ball from the round.

( 1) Percent rebound means the percentage of the dropped height the ballwill rebound when dropped a distance of 10 inches onto a 1 inch thicksteel plate.

(2) One drop of the guillotine blade was sufficient to cut the cover ofthe ball and expose the elastic thread winding.

(3) First impact distorted the conventional ball and caused loss ofcompression due to breakage of elastic thread windings. Commonly,successive tests caused complete breakage of threads and rupture of ballcenter. The numbers indicated for the balls of the present inventionshow the number of tests necessary to break the ball into two pieces.Prior to this breakage, only scuffing and slight loss of compression wasevident.

While the present invention relates most particularly to the use of thenovel composition of matter as a unitary molded golf ball, otherextensive applications may also be mentioned. These include, forexample, the manufacture of printing plates, coverings for rolls or themanufacture of rolls per se, protective bumpers, bowling balls,insulators, floor tiles, shoe soles and heels, battery boxes, solidtires and the like. It will be obvious to those skilled in the art thata wide range of applications are possible for the composition of theinvention where properties of resilience, toughness and high impactresistance are required.

What we claim is:

l. A composition of matter comprising essentially a cured blend of (1)an elastomer capable of being crosslinked by peroxide-initiatedpolymerization selected from the group consisting of cis-l,4-polybutadine, polyisoprene, ethylene propylene non-conjugateddiolefin terpolymers, styrene/butadiene rubbers, nitrilebutadienerubbers and mixtures thereof, (2) an epoxy resin selected from the groupconsisting of cycloaliphatic epoxy resins, epoxy novolac resins,epichlorohydrin-4,4-resins and mixtures thereof, (3) an epoxy resincuring agent or hardener selected from citraconic acid, itaconic acid,fumaric acid, maleic acid, maleic anhydude and mixtures thereof, (4) acrosslinking catalyst for said elastomer and (5) a filler material.

2. A composition of matter as claimed in claim 1 also containing anepoxy resin curing accelerator.

3. A composition of matter as claimed in claim 1 also containing acoloring pigment.

4. A composition of matter as claimed in claim I wherein thecrosslinking catalyst is of the free radical or peroxide type.

5. A composition of matter as claimed in claim 1 wherein the fillermaterial is selected from the group consisting of silica, clays,carbonates, talc, metal oxides, asbestos, glass, particulate syntheticplastics, particulate carbonaceous materials and mixtures thereof.

6. A composition of matter as claimed in claim 2 wherein the epoxy resincuring accelerator is selected from the group consisting of stannousoctoate, dimethylaminomethylphenol, tri(di-methylaminomethyl) phenol,Lewis acids and mixtures thereof.

7. A composition of matter as claimed in claim 1 wherein the epoxy resincuring agent or hardener is selected from fumaric acid, maleic acid,maleic anhydride and mixtures thereof. 7

8. A unitary molded golf ball of improved cut and impact resistancehaving a maximum diameter of about 1.69 inches comprising parts byweight of an elastomer capable of being cross-linked byperoxide-initiated polymerization selected from the group consisting ofcis-l,4-polybutadiene, polyisoprene, ethylene propylene non-conjugateddiolefin terpolymers, styrene/butadiene rubbers, acrylonitrile/butadienecopolymers and mixtures thereof, from about 20 to about 45 parts byweight of an epoxy resin selected from the group consisting ofcycloaliphatic epoxy resins, epoxy novolac resins,epichlorohydrin-4,4'-dihydroxydiphenyl-dimethylmethane resins andmixtures thereof, from about 5 to about 20 parts by weight of an epoxyresin curing agent or hardener selected from citraconic acid, itaconicacid, fumaric acid, maleic acid, maleic anhydride and mixtures thereof,from about 20 to about 45 parts by weight of a filler and from about 0.5to

about parts by weight of a cross-linking catalyst for said elastomer.

9. A golf ball as claimed in claim 8 wherein the epoxy resin is acyclo-aliphatic epoxy resin and the epoxy resin curing agent or hardeneris selected from fumaric acid, maleic acid, maleic anhydride andmixtures thereof.

10. A golf ball as claimed in claim 9 also containing from about 0.1 toabout 0.5 part by weight of an epoxy resin curing accelerator.

11. A golf ball as claimed in claim 9 also containing from I about 0.5to about 10 parts by weight of a coloring pigment.

12. A golf ball as claimed in claim 9 wherein the crosslink-

2. A composition of matter as claimed in claim 1 also containing anepoxy resin curing accelerator.
 3. A composition of matter as claimed inclaim 1 also containing a coloring pigment.
 4. A composition of matteras claimed in claim 1 wherein the crosslinking catalyst is of the freeradical or peroxide type.
 5. A composition of matter as claimed in claim1 wherein the filler material is selected from the group consisting ofsilica, cLays, carbonates, talc, metal oxides, asbestos, glass,particulate synthetic plastics, particulate carbonaceous materials andmixtures thereof.
 6. A composition of matter as claimed in claim 2wherein the epoxy resin curing accelerator is selected from the groupconsisting of stannous octoate, dimethylaminomethylphenol,tri(di-methylaminomethyl) phenol, Lewis acids and mixtures thereof.
 7. Acomposition of matter as claimed in claim 1 wherein the epoxy resincuring agent or hardener is selected from fumaric acid, maleic acid,maleic anhydride and mixtures thereof.
 8. A unitary molded golf ball ofimproved cut and impact resistance having a maximum diameter of about1.69 inches comprising 100 parts by weight of an elastomer capable ofbeing cross-linked by peroxide-initiated polymerization selected fromthe group consisting of cis-1,4-polybutadiene, polyisoprene, ethylenepropylene non-conjugated diolefin terpolymers, styrene/butadienerubbers, acrylonitrile/butadiene copolymers and mixtures thereof, fromabout 20 to about 45 parts by weight of an epoxy resin selected from thegroup consisting of cycloaliphatic epoxy resins, epoxy novolac resins,epichlorohydrin-4,4''-dihydroxydiphenyl-dimethylmethane resins andmixtures thereof, from about 5 to about 20 parts by weight of an epoxyresin curing agent or hardener selected from citraconic acid, itaconicacid, fumaric acid, maleic acid, maleic anhydride and mixtures thereof,from about 20 to about 45 parts by weight of a filler and from about 0.5to about 5 parts by weight of a cross-linking catalyst for saidelastomer.
 9. A golf ball as claimed in claim 8 wherein the epoxy resinis a cyclo-aliphatic epoxy resin and the epoxy resin curing agent orhardener is selected from fumaric acid, maleic acid, maleic anhydrideand mixtures thereof.
 10. A golf ball as claimed in claim 9 alsocontaining from about 0.1 to about 0.5 part by weight of an epoxy resincuring accelerator.
 11. A golf ball as claimed in claim 9 alsocontaining from about 0.5 to about 10 parts by weight of a coloringpigment.
 12. A golf ball as claimed in claim 9 wherein the crosslinkingcatalyst is of the free radical or peroxide type.
 13. A golf ball asclaimed in claim 9 wherein the filler material is selected from thegroup consisting of silica, clays, carbonates, talc, metal oxides,asbestos, glass, particulate synthetic plastics, particulatecarbonaceous materials and mixtures thereof.
 14. A golf ball as claimedin claim 13 wherein the epoxy resin curing accelerator is selected fromthe group consisting of stannous octoate, dimethylaminomethylphenol,tri(dimethylaminomethyl) phenol, Lewis acids and mixtures thereof.